Method of controlling admission of fuel and air to blast furnaces



Jan. 12, 1965 F. KENNEDY 3,

METHQD 0F CONTROLLING ADMISSION OF FUEL AND AIR T0-BLAST FURNACES Filed Feb. 14, 1961 2 Sheets-Sheet 1 INVENTOR FRANK KENNEDY A Ilorney Jan. 12, 1965 F. KENNEDY METHOD OF CONTROLLING ADMISSION OF FUEL AND AIR TO BLAST FURNACES 2 Shee ts-Sheet 2 Filed Feb. 14, 1961 United States Patent 3,165,399 METHOD (3F CONTROLLING ADMESION 0F FUEL AND AER T0 BLAST FURNACES Frank Kennedy, Johnstown, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Filed Feb. 14, 1961, Ser. No. 39,166 It) Claims. (Cl. 75-42) This invention relates to a method of controlling admission of fuel to blast furnaces and more particularly to controlling the admission of fuels such as natural gas, oil, or powdered coal into the tuyeres of the blast furnace. The broad concept of supplying fuel in this manner to replace part of the coke charge is known and the advantages thereof are also known. However, the various methods suggested and used for introducing such fuel have various disadvantages. In general, such controls regulate the flow of gas to the tuyeres based on a percentage of total air flow to all the tuyeres. In blast furnace operation the furnace burden is subject to variations which frequently restrict the flow of air through one or more tuyeres. This reduced flow of air lowers the rate of combustion in the region of the restricted tuyere and may produce a localized cooling. If the flow of natural or coke oven gas or other fuel through the restricted tuyere is not decreased, the rate of cooling at the restricted tuyere is increased so that the troubles at this point are multiplied. Other disadvantages of other methods relate to safety and rapidity of operation.

It is therefore an object of my invention to provide a method of operating a blast furnace in which air and fuel are introduced into the tuyeres and in which a predetermined air-fluel ratio is maintained for both total flow and flow to the individual tuyeres.

Another object is to provide such a method in which the fuel gas to the tuyeres is shut off when the air pressure is higher than the gas pressure.

A still further object is to provide such a method in which fuel flow to the individual tuyeres is shut off when the air flow to that tuyere falls below a predetermined amount.

These and other objects will be more apparent after referring to the following specification and attached drawings, in which:

FIGURE 1 is a schematic plan view of a blast furnace and the fuel and air supply thereto;

FIGURE 2 is a schematic view of apparatus suitable for the practice of my invention; and

FIGURE 3 is a schematic wiring diagram.

Referring more particularly to the drawings, reference numeral 2 indicates a blast furnace having "a plurality of tuyeres 4 arranged around its periphery. Air is supplied to each of the individual tuyeres from a bustle pipe or air manifold 6 through a conduit 8. The air is supplied to the bustle pipe from a stove 10. Cold air is delivered to the stove 10 through a cold blast main 12 having a snort valve 14 associated therewith. The parts so far described are conventional. According to my invention a fuel gas manifold 16 also surrounds the blast furnace 2 with individual conduits 1% leading from the manifold 16 to each individual tuyere. Assuming that the fuel is gas, it is supplied to the manifold 16 through a gas main 20 having a pressure regulator 22 therein for maintaining the gas pressure constant. An orifice 24 is 3,lh5,3 Patented Jan. 12, 1965 provided in the cold blast main 12 and a standard flow transmitter 26, such as a Model llC25 pneumatic type manufactured by Moore Products Company of Philadelphia, Pennsylvania, is connected to opposite sides of the orifice so as to get an impulse proportional to gas flow. A pressure tap 28 is connected to the cold blast main and is connected to a standard pressure transmitter 39, such as a Moore Model 1735 pneumatic type. A thermocouple 32, or other temperature responsive device, is also provided in the gas main l2 and is connected to a standard temperature transmitter 34, such as a Moore Model 33380. The impulse from transmitter 26 is modified by the impulse from pressure transmitter 30 by means of a standard pressure compensated impulse relay 36, such as a Sorteberg Type SP having square root extraction, so as to compensate for pressure differentiations and the impulse from relay 36 is modified by an impulse from transmitter 34 by means of a standard compensated impulse relay 38, such as a Bailey Type AR8062A, in order to compensate for temperature changes of the air blast. The impulse from relay 38 is modified in a standard differential comparison relay 4%, such as a Moore Model 68-1, by an impulse from a standard position transmitter 4 2, such as a Bailey Model 5318487A3, which last named impulse is proportional to the opening of snort valve 14. The impulse from relay 40 is delivered to a standard flow meter and recorder 44, such as a Moore Model 5321R, which records the total flow of air to the blast furnace compensated for temperature and pressure. The impulse from relay 40 is also impressed on "a standard pneumatic set ratio relay 46, such as a Sorteberg Type R, which in turn is connected to a standard air-gas ratio controller 48, such as a Moore Model 50M Nullmatic Controller. While the instruments so far described are air operated they may be replaced by other types of standard instruments which may be oil or electrically operated.

An orifice 50 is provided in the gas main 20 and a How transmitter 52 is connected thereacross. The transmitter 52 may be the same type as transmitter 56 but it is preferred to use a Moore Model l1C-l00 in place thereof. A pressure transmitter 54, temperature transmitter 56, pressure compensating impulse relay 58 and temperature compensating relay 60 corresponding to de vices 3t), 34, 36, and 38, respectively, are connected to transmitter 52 in the same manner as devices 36, 34, 35 and 33 are connected to transmitter 26. Temperature compensating relay 60 has its impulse connected to recorder 44 and to air-gas ratio controller 48. The impulse from ratio controller 48 is connected to manual automatic selector 62 which is a standard type such as Moore Model 524-1 and then to a standard selector relay 64, such as a Moore Model 58 which is used to modify the signal at low gas flow to prevent total shut-off of the gas. The pneumatic signal from relay 64 is connected to a solenoid operated three-way valve as which may be positioned to pass air to the atmosphere or to diaphragm 68D which acts to position gas control valve 68.

Locatedin each of the conduits 18 leading to the individual tuyeres is an air operated shut-off valve 70 and an orifice 72 for measuring gas flow. The position of valve 70 is controlled by a diaphragm 70D. A fluid transmitter 7d of any standard type such as Hagan Model MYP-SIO 335430-L(NP) is connected across the orifice 72. The impulse transmitter 74 is connected to pressure switch 76. An air flow transmitter '78, such as a Moore Model ll-C-25, is connected across bustle pipe 6 and conduit 8. The output of impulse transmitter 73 is connected to a standard high-low pressure switch having a dual setting, such as a Barksdale Melatron Model 424 E-lO-L, and also to a standard impulse relay 82, such as a Moore Model 6725, and then to a solenoid operated three-way valve 84 which either delivers the impulse to diaphragm 70D or vents it to asmosphere. It will be understood that each of the tuyeres is provided with this equipment although only one is shown and described.

An air pressure switch 86 is connected to the hot blast main 6 and a gas pressure switch 88 is connected to the gas main 20. The switches 86 and 88 are connected in series with a similar switch 90 connected to the instrument air manifold (not shown) and also in series with a relay coil 92 having normally open contacts 92C and 92(31. Contact 92C is connected in parallel with a momentary contact switch 94. A similar push button switch 96 is connected in series with switches 86, 88, and 9%. Contact 92Cl is connected in series with solenoid 66S of I valve 66. A differential pressure switch 98, which is connected between hot blast manifold 43 and gas main 24), is arranged in series with momentary contact switches 100 and N2 and relay coil 104 having normally open contacts INC and lMCll. Contact 104C is connected in parallel with switch 1%. Contact 1624GT is connected in series with switches '76, 80 and 106 and relay coil 10% having a normally open contact 108C which is connected in series with solenoid 848. At least part of the circuit connected in series with contact lltMCll is repeated for the other tuyeres and additional contacts may be provided for relay T04 to control the circuits if desired or all of the other circuits can be arranged in series with contact 104C}.

In operation, the various instruments are set to suit the desired conditions. The air-gas ratio controller 48 will maintain the desired ratio between air and gas flow by changing the opening and closing of valve 68, compensated signals from air flow transmitter 26 and gas flow transmitter 52 controlling feed-back to ratio controller 48 to insure that the valve 66 is properly positioned. Switches 94 and 96 are closed and if the instrument air, hot blast air and the fuel gas are at above a pre-set minimum pressure, the switches 86, 8S and 99 will also be closed so that relay coil 92 will be energized. Energization of coil 92 closes contact 920 to lock coil 92 in when switch 94 is released. Closing of contact @ZCll energizes solenoid 668 so as to position valve as to admit the control signal to diaphragm 681) of valve 68. Thus, valve 68 is positioned to maintain the predetermined ratio between air and gas. However, if the pressure of the instrument air, hot blast air or gas falls below the preset pressure, the corresponding pressure switch will open to deenergize' relay coil F92. This opens contact 92C1 to deenergize solenoid 668 which will position valve 66 to vent the signal from relay 64- to atmosphere. Thus, the control is taken out of operation. take the control out of operation.

In controlling the fiow of fuel gas to the individual tuyeres, switch 98 is closed as long as the supply gas pressure is higher than the manifold air pressure. To start the control in operation switch 100 is momentarily closed which will energize relay coil 104 since switches 98 and H52 are closed. Energization of coil 1434 closes contact Iltl-tC to lock it in. Closing of contact ltl tCll will energize relay coil 108 if switches 76, St) and 106 are closed. If the air flow to the particular tuyere is low due to plugging of other cause, the output signal of its associated transmitter 78 will be of low magnitude and the signal will modulate the valve 70 through relay 82 to a partially closed position. This cut back of gas flow will be proportional to the reduction in air flow until the Opening of switch 96 will also air flow to the tuyere is reduced to percent of normal. If the signal continues to'decrease due'to air flow below 50 percent, the valve will close at a more rapid rate. If the air flow continues to decrease, the pressure switch $9 will open if the air flow is reduced to about /5 the normal flow. This will deenergize relay coil 1G8 and close its contact 198C to deenergize solenoid 845 which will actuate valve 84 to vent the impulse to atmosphere and thus close valve 70 to cut off flow of all gas to the plugged tuyere. The gas flow from plugged tuyeres automatically is diverted to the remaining tuyeres. If a tuyere is ruptured the gas flow will increase greatly and the output signal of transmitter 73 will be of such high magnitude that pressure switchlstl will open with the associated valve 7t closing and the gas being diverted to those tuyeres operating normally. If there isa break in the hose connection between orifice 72 and its associated tuyere, the gas flow through orifice 72 will increase, thus opening switch .76 to deenergize relay N8 which deenergizes solenoid 843. This causes valve S tto vent and shut off valve 76. Manual re-set provided as part of switch 76' prevents automatic re-opening of the valve 70. The switch 1% can be opened if necessary to remove gas from an individual tuyere. Opening of switch m2 takes all the'controls of the fuel gas to the individual tuyeres out of operation.

While one embodiment of my invention has been shown and described it will be apparent that other adaptations and modifications may be madewithout departing from the scope of the following claims.

I claim:

1. The method of operating a blast furnace having a plurality of tuyeres which comprises introducing air and fuel separately, into the tuyeres, maintaining a predetermined ratio between total air flow and total fuel flow,

' maintaining the samepredetermined ratio between air and fuel to each tuyere as for totalair and fuel flow, decreasing the fuel HOW to an individual tuyere when the air flow to that tuyere decreases, and distributing the fuel diverted from said last mentioned tuyere to the other tuyeres.

2. The method of operating a blast furnace according to claim 3 in which the fuel to the individual tuyeres is shut oif when the air flow to the associated tuyere falls below a predetermined amount.

3. The method of operating a blast furnace according .to claim 1 in which the fuel is shut off when the pressure of said total air or total fuel falls below a predetermined amount.

4. The method of operating asblast furnace according to claim 1 in which the fuel to the individual tuyeres is shut off when. the air flow to the associated tuyere falls below a predetermined amount.

5. The method of operating a blast furnace having a plurality of tuyeres which comprises introducing air and gas separately into the tuyeres, maintaining a predetermined ratio between total air flow and total gas flow, maintaining the same predetermined ratio between air and gas ratio to each tuyere as for total air and gas flow, decreasing the gas flow to an individual tuyere when the air fiow to that tuyere deceases, and distributing the gas diverted from said last mentioned tuyere to trauma tuyeres. 7

6. The methodof operatinga blast furnace according to claim 5 in which the gas to all of said tuyeres is shut off when the total air pressure is higher than the total gas pressure.

7. The method of operating a blast furnace according to claim 5 in which the gas to the individual tuyere is shut off when the air flow to the associated tuyere falls below a predetermined amount, and the gas to all of said tuyeres is shut off when the total air pressure is higher than the total gas pressure. 7

8. The method of operating a blast furnace according to claim 5 in which the gas is shut off when the pressure of said total air or gas falls below a predetermined amount.

9. The method of operating a blast furnace according to claim 8 in which the gas to all of said tuyeres is shut ofi? when the total air pressure is higher than the total gas pressure.

10. The method of operating a blast furnace according to claim 5 in which the gas to the individual tuyere is shut off when the airflow to the associated tuyere falls below a predetermined amount, and the gas to all of said tuyeres is shut 01f when the total air pressure is higher than the total gas pressure.

6 References Cited by'the Examiner UNITED STATES PATENTS 2,420,398 5/47 Kenney 75-42 2,690,333 9/ 54 Pomykala 266--29 2,719,083 9/55 Pomykala 75--42 2,879,056 3/59 Wagner 266-29 OTHER REFERENCES Blast Furnace, Coke Oven, and Raw Materials Pro- 10 ceedings, 1960, vol. 19, pages 242-253 and 288-292.

DAVID L, RECK, Primary Examiner.

MARCUS U. LYONS, RAY K. WINDHAM, Examiners. 

1. THE METHOD OF OPERATING A BLAST FURNACE HAVING A PLURALITY OF TUYERES WHICH COMPRISES INTRODUCING AIR AND FUEL SEPARATELY INTO THE TUYERES, MAINTAINING A PREDETERMINED RATIO BETWEEN TOTAL AIR FLOW AND TOTAL FUEL FLOW, MAINTAINING THE SAME PREDETERMINED RATIO BETWEEN AIR AND FUEL TO EACH TUYERE AS FOR TOTAL AIR AND FUEL FLOW, DECREASING THE FUEL FLOW TO AN INDIVIDUAL TUYERE WHEN THE AIR FLOW TO THAT TUYERE DECREASES, AND DISTRIBUTING THE FUEL DIVERTED FROM SAID LAST MENTIONED TUYERE TO THE OTHER TUYERES. 